Window assembly and lower saw guard for circular saw

ABSTRACT

A window assembly is provided for use on a hand-held circular saw. The window assembly has a transparent member that is attached to an upper guard of the saw. The transparent member has a forward edge and a rearward edge and slopes downwardly to form a rearwardly facing acute angle with respect a planar base of the saw. The acute angle has a minimum value to prevent light from overhead sources from reflecting into the user&#39;s eyes and has a maximum value to prevent light from forward light sources from reflecting into the user&#39;s eyes. The forward edge of the transparent member is located rearwardly of the point at which a predetermined line intersects the guard. Additionally, a lower blade guard is provided for use on a circular saw having a clear viewing window on the upper blade guard. The lower blade guard has a truncated portion that allows a line of sight between the workpiece being sawed and the clear viewing window even when the lower guard is in a fully retracted position.

BACKGROUND OF THE INVENTION

This invention relates to a circular saw having a viewing window on theupper guard.

One of the problems associated with the use of a hand-held circular sawis properly aligning the saw so that the desired cut is achieved.Typically, a user will draw a line on the material to be cut. This linerepresents the location of the desired cut. The problem arises when theuser of the hand-held circular saw attempts to align the blade with theline on the material. The problem continues as the user attempts to keepthe blade tracking on the desired cut line.

To assist in the alignment, circular saws are typically provided with aguide slot. The guide slot is usually located on the planar cutting baseof the saw, and is positioned in front of, and in line with, thecircular saw blade. The user then positions the saw so that the line onthe material appears in the guide slot. While the provision of such aguide slot does aid the user in proper saw alignment, problems stillexist. First, because the guide slot is located in front of the blade,if the saw blade is not perpendicular relative to the workpiece, theguide slot can be positioned on the cut line while the blade is not. Ifthe user begins to cut the material with the saw in this orientation, itis often difficult to correct the alignment problem. Second, because theblade is covered by a saw guard, the user cannot see the blade as itexits the material, and therefore cannot directly monitor the travel ofthe blade.

Attempts have been made to allow the user of the saw to view the bladeas it exits the material, thereby allowing the user to properly guidethe blade along the desired cut line. A device that allows a user toview the blade is disclosed in U.S. Pat. No. 4,450,627. This patentdiscloses a circular saw with a viewing window on the upper saw guard.The window is intended to allow users of the saw to properly align thesaw to the workpiece by allowing them to view the blade. While thisviewing window solves the above problems to some degree, its positioningremains a problem.

If the viewing window is not properly positioned, the user will beunable to see the blade exiting the material due to the reflection oflight by the transparent section of the viewing window. To compensate,the user may attempt to reposition the light source, such as aflashlight, or may reposition himself relative to the saw. Thisrepositioning can affect efficiency as well as the quality of the workbeing performed. If the user repositions himself relative to the saw,the resulting position may be an uncomfortable one from which to operatethe saw. Further, the trial and error necessary to find the properposition of saw, user and light source wastes the user's time.

The position of the viewing window must also account for the sawdustgenerated as the saw cuts through the workpiece. If the window ispositioned to far forwardly, the sawdust can accumulate on thetransparent section of the window and impair the user's view of theblade as it exits the workpiece. The viewing window must therefore bepositioned so as to minimize or eliminate the accumulation of sawdust onthe viewing window.

Further, circular saws having a viewing window have heretofore notadequately addressed the problem caused by the lower saw guard inrelation to the provision of a viewing window. The lower saw guardsurrounds the lower portion of the blade when the saw is not in use.When the saw is being used, the front portion of the lower saw guardengages the workpiece and is rotated upwardly to expose the lowerportion of the blade. When the lower guard is rotated fully upwardly,the rear portion of the lower saw guard can impair the user's view ofthe blade through the transparent section of the viewing window. Thisimpairment does not affect the user's view as the cut is initiated, butrather impairs the view when the saw is sufficiently engaged with theworkpiece so as to rotate the lower guard to a fully retracted position.

Therefore, a window assembly is needed that is properly positioned inthe upper saw guard of a circular saw so that the user can view, from anormal operating position, the blade exiting the workpiece. A windowassembly is needed that minimizes any light reflected into the eyes ofthe user from both above and in front of the viewing window. Further, awindow assembly is needed that is properly positioned in the upper sawguard of a circular saw so that the accumulation of sawdust on theviewing window is reduced or eliminated. Finally, a lower saw guard isneeded which will allow a user to view the saw blade exiting theworkpiece, through a transparent member of the window assembly in theupper saw guard, even when the lower guard is in a fully retractedposition.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide awindow assembly in the upper guard of a circular saw positioned so as tominimize any light reflected into the eyes of the person using the saw.

It is another object of the present invention to provide a windowassembly located rearwardly of a predetermined point to minimizeaccumulation of sawdust on the window assembly.

A further object of this invention is to provide a window assemblyhaving a transparent member oriented at an angle greater than a minimumangle of inclination of the viewing window relative to the workpiece.

A still further object of this invention is to provide a window assemblyhaving a transparent member oriented at an angle less than a maximumangle of inclination of the viewing window relative to the workpiece.

Yet another object of the invention is to provide a lower saw guard, tobe used on a circular saw with a viewing window, that will not obstructthe view through the transparent member of the window even in a fullyretracted position.

According to the present invention, the foregoing and other objects areobtained by a window assembly for use on a hand-held circular saw. Thewindow assembly has a transparent member that is attached to an upperguard of the saw, and that has a top surface, a forward edge and arearward edge. The transparent member slopes downwardly to form arearwardly facing acute angle with respect to a planar base of the saw.The acute angle has a minimum value which prevents light from overheadsources from reflecting into the user's eyes and has a maximum valuewhich prevents light from forward light sources from reflecting into theuser's eyes. In another aspect of the invention, the forward edge of thetransparent member is located where a predetermined line intersects theguard. This location prevents sawdust from accumulating on thetransparent member. In still another aspect of the invention, a lowerblade guard is provided for use on a circular saw having a clear viewingwindow on the upper blade guard. The lower blade guard has a truncatedportion that allows a line of sight between the workpiece being sawedand the transparent member of the window assembly even when the lowerguard is in a fully retracted position.

To locate the forward-most point of the transparent member of the windowassembly, a line is constructed extending tangentially away from theblade at the point at which the saw blade exits the workpiece. This lineintersects the upper blade guard. The window is placed rearwardly ofthis intersection point.

To establish the minimum angle of inclination for the transparent memberof the window assembly, a first line is constructed from the point atwhich the blade exits the workpiece to the rear edge of the transparentmember of the window assembly. A second line is then constructedextending horizontally outward from the rear edge of the top surface ofthe transparent member. A third line is constructed bisecting the angleformed by the previous two lines. This third line establishes theminimum angle of inclination for the top surface of the transparentmember.

To establish the maximum angle of inclination for the transparent memberof the window assembly, a first line is constructed as above.Thereafter, a forward point is located six inches in front of the pointat which the blade exits the workpiece. A second line is constructedfrom this forward point to the rear edge of the transparent member. Athird line is then constructed bisecting the angle formed by the firstand second lines. This third line represents the maximum angle ofinclination for the top surface of the transparent member.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings which form a part of this specification andwhich are to be read in conjunction therewith and in which likereference numerals are used to indicate like parts in the various views:

FIG. 1 is a front perspective view showing a properly located windowassembly of the present invention attached to the upper guard of acircular saw;

FIG. 2 is a side elevation view of the saw of FIG. 1 showing the lowerguard in a fully retracted position;

FIG. 3 is an enlarged partial top plan view taken along line 3-3 of FIG.2, with part of the transparent member being broken away to showparticular details of construction;

FIG. 4 is an enlarged partial perspective view taken along line 4--4 ofFIG. 3 showing the lower guard in a fully retracted position;

FIG. 5 is a schematic view of the saw of FIG. 1, illustrating the methodof calculating the minimum angle of inclination for the transparentmember of the window assembly; and

FIG. 6 is a schematic view similar to FIG. 5, illustrating the method ofcalculating the maximum angle of inclination for the transparent memberof the window assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in greater detail, and initially to FIG. 1, apower circular saw designated generally by numeral 10 is shown. Saw 10has a motor 12 which is operably attached to a circular saw blade 14. Apower cord (not shown) supplies electrical power to motor 12. The upperportion of blade 14 is surrounded by an upper saw guard 18. Upper guard18 is fixedly secured to motor 12. The lower portion of blade 14 issurrounded by a lower saw guard 20. Saw 10 further has a planar base 21with an alignment notch 23.

Lower guard 20 exposes the lower portion of blade 14 in a manner that iswell-known in the art. More specifically, the front edge 22 of lowerguard 20 engages the leading edge of a workpiece 24. As the saw passesfurther into workpiece 24, lower guard 20 is rotated generally upwardlyto expose the lower portion of the blade. Guard 20 is spring loaded sothat when saw 10 is disengaged from workpiece 24, lower guard 20 returnsto its lower, blade covering position.

Upper guard 18 is provided with a viewing window assembly 25. Windowassembly 25 has a transparent member 26 which is held in place on guard18 by a window frame 27. Transparent member 26 allows the user of saw 10to view blade 14 as it exits workpiece 24, thereby allowing the user toproperly align, and maintain alignment, of saw 10.

Transparent member 26 must be properly positioned on guard 18 to allowthe user of saw 10 to properly align and monitor the travel of blade 14.First, the forward-most position of transparent member 26 on guard 18must be determined. Locating transparent member 26 beyond the properforward-most position can result in the sawdust generated by blade 14accumulating on transparent member 26. If sawdust accumulates ontransparent member 26, either transparent member 26 must be cleaned orthe user's view through transparent member 26 will be obstructed bysawdust. Further, the proper angle of inclination of transparent member26 must be determined and used. Generally, there is a range between aminimum angle of inclination and a maximum angle of inclination that maybe used. If transparent member 26 has an angle of inclination differentfrom the angles calculated in the manner described below, the user'sview through transparent member 26 will be impaired by light reflectingfrom the top surface of transparent member 26.

In order to determine the forward-most position of transparent member 26on guard 18, the point at which blade 14 exits workpiece 24 is firstlocated. This point is designated in the drawings by reference numeral28. The cutting depth for blade 14 can be adjusted by repositioningplanar base 21 so that thinner or thicker workpieces may be sawed.Manufacturers typically ship saw 10 with blade 14 at its maximum cuttingdepth. In determining exit point 28, blade 14 should be set at maximumdepth which is the most common depth utilized by saw users. As shown inFIG. 2, from point 28, a line is constructed extending tangentially awayfrom blade 14 and upwardly towards guard 18. This tangential line isdesignated in the drawings by the reference numeral 30. The point atwhich line 30 intersects guard 18 defines the maximum forward-most pointat which the forward edge of transparent member 26 should be positioned.This intersection point is defined in the drawings by reference numeral32. Locating transparent member 26 at or behind intersection point 32ensures that transparent member 26 is located behind the main path ofthe dust particles generated by blade 14 when saw 10 engages workpiece24. Such a location will decrease the need and frequency at whichtransparent member 26 must be cleaned. Therefore, locating transparentmember 26 rearwardly of intersection point 32 increases the ability ofthe user of saw 10 to view blade exit point 28 without having the viewobstructed or impaired by sawdust particles.

Having properly located the forward-most point for transparent member26, the proper angles of inclination of transparent member 26 must alsobe determined. Referring to FIG. 5, to determine the minimum angle ofinclination, a line is constructed between blade exit point 28 and therear edge of transparent member 26. Again, this line is constructed withblade 14 at its maximum cutting depth. The rear edge of transparentmember 26 is located on guard 18 to allow a line of sight between theuser in a normal saw operating position and blade exit point 28. Theline between blade exit point 28 and the rear edge of transparent member26 is shown in the drawings by reference numeral 34. The point at whichline 34 intersects guard 18 and the rear edge of the top surface oftransparent member 26 is shown in the drawings by reference numeral 36.A second line 38 is constructed extending from point 36 outwardly fromguard 18. Line 38 is constructed to be horizontal so that it will besubstantially parallel to workpiece 24 and planar base 21. A third line40 is constructed and extends from point 36 downwardly between lines 34and 38. Line 40 is constructed so as to bisect the angle formed by firstline 34 and line 38. Line 40 establishes the minimum angle ofinclination, indicated by α in the drawings, for transparent member 26.Therefore, the angle formed by the plane of the top surface oftransparent member 26 relative to workpiece 24 should be no less thanthe acute angle α established between line 40 and workpiece 24. Whentransparent member 26 has an angle of inclination equal to or greaterthan this minimum angle, only light originating from below line 38 iscapable of reflecting into the eyes of the user.

Any light originating from above line 38, such as from a ceiling light,will reflect away from the user's eyes.

Having determined the minimum angle of inclination, the maximum angle ofinclination for transparent member 26 can be determined as outlinedbelow, with reference to FIG. 6, to establish the range of angles thatmay be used for transparent member 26. In determining the maximum angleof inclination, first line 34 is constructed in the same manner as fordetermining the minimum angle of inclination. Therefore, point 36 isdetermined in the same fashion with blade 14 at its maximum depth. Next,a forward point 42 is located six inches directly in front of blade exitpoint 28, in a line extending from, and in line with, blade 14. Forwardpoint 42 represents the distant edge of a typical workpiece 24, theimportance of which is more fully discussed below. A fourth line 44 isconstructed connecting forward point 42 with intersection point 36.Thereafter, a fifth line 46 is constructed bisecting the angle formed byfirst line 34 and fourth line 44. Fifth line 46 establishes the maximumangle of inclination of transparent member 26, indicated by β in thedrawings. Therefore, the angle formed by the plane of transparent member26 relative to workpiece 24 should be no greater than the acute angle βestablished between line 46 and workpiece 24. Workpiece 24 is oftenlight in color and thus can reflect a considerable amount of light. Whentransparent member 26 has an angle of inclination equal to or less thanthis maximum angle 62, the operator will only be able to see areflection of the top surface of workpiece 24 from about point 42 andbeyond. Therefore, because the typical workpiece is approximately sixinches wide, orienting transparent member 26 with an angle ofinclination equal to or less than the acute angle β prevents themajority of light reflected from workpiece 24 from reaching the user'seyes. Thus, the user will be better able to view the blade exit point asthe cut is made.

By locating transparent member 26 rearwardly of point 32 and between theminimum angle of inclination α and the maximum angle of inclination β asdetermined above, transparent member 26 will be located in a positionwhich minimizes any obstruction caused by sawdust, and which allows theuser to view exit point 28 through transparent member 26 without his orher vision being obstructed by unwanted reflections from the top surfaceof transparent member 26.

In an alternative embodiment, transparent member 26 is oriented with anangle of inclination equal to or greater than the acute angle α. In thisembodiment an opaque vertical rib 47, shown in dashed lines in FIG. 6,is attached to upper guard 18 adjacent the forward edge of transparentmember 26. Again, orienting transparent member 26 at an angle greaterthan acute angle a prevents light from overhead sources from reflectinginto the user's eyes. Rib 47 extends outwardly from upper guard 18 andthus prevents light from any forward light sources from reflecting intothe user's eyes. Rib 47 could also extend along the sides of transparentmember 26 if it is desired to block light sources from the sides. Thus,the orientation of transparent member 26, at an angle greater than theminimum angle of inclination, and rib 47 operate to block unwantedreflections so that the user can view exit point 28 through transparentmember 26.

As outlined above, a properly positioned window assembly having atransparent member allows the user of saw 10 to view workpiece 24 freeof unwanted reflections and sawdust obstructions. However, even with aproperly positioned window assembly, the user's view of the point atwhich the blade exits the workpiece can be obstructed by the lowerguard. Such an obstruction can result when the lower guard is in a fullyrotated position. Therefore, lower guard 20 of the present invention hasa truncated portion 48 on a rear section of lower guard 20, as best seenin FIGS. 3 and 4. Truncated portion 48 allows the user of saw 10 to viewblade 14 as it exits the workpiece, even when lower guard 20 is in afully retracted position, as shown in FIGS. 2 and 3. A line of sight ismaintained through transparent member 26 to blade exit point 28, asillustrated by reference line 51 in FIG. 2.

Lower guard 20 has a perimeter wall 52 that extends between an innerside 54 and an outer side 56. Truncated portion 48 is formed as a"cut-out" from perimeter wall 52 and inner side 54, as best seen inFIGS. 3 and 4. Truncated portion 48 has an inner edge 58 extendingperpendicularly from inner side 54 of lower guard 20. Inner edge 58terminates at an outer edge 60. Outer edge 60 extends from inner edge 58to a rear edge 62 of perimeter wall 52. Outer edge 60 is tapered towardsouter side 56 as best seen in FIG. 3. Inner edge 58 and outer edge 60define the area through which a line of sight is provided, thus allowingthe user to view blade exit point 28 even when lower guard 20 is in afully retracted position. It should be noted that inner edge 58 couldextend to outer side 56, thus eliminating outer edge 60. Such astructure would still provide a line of sight to workpiece 24 throughtransparent member 26, but would offer less coverage of blade 14 whenlower guard 20 is in a normal, blade covering position.

In use, the user of saw 10 places planar base 21 on workpiece 24 andpositions saw 10 so that the desired cut line is within alignment notch23. The user then aligns saw 10 so that the front edge of blade 14 isalso on the desired cut line. The user can view blade 14 for thispurpose through transparent member 26. As the user begins to sawworkpiece 24, lower guard 20 is rotated upwardly. The user cancontinually monitor the point at which blade 14 exits the workpiece byviewing this point through transparent member 26. As the user saws intoworkpiece 24, lower guard 20 will eventually be in a fully retractedposition. The user can monitor blade exit point 28 even when lower guard20 is in this fully retracted position due to truncated portion 48.

From the foregoing, it will be seen that this invention is onewell-adapted to attain all the ends and objects hereinabove set forthtogether with other advantages which are obvious and which are inherentto the structure. It will be understood that certain features andsubcombinations are of utility and may be employed without reference toother features and subcombinations. This is contemplated by and iswithin the scope of the claims. Since many possible embodiments may bemade of the invention without departing from the scope thereof, it is tobe understood that all matter herein set forth or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

We claim:
 1. A window assembly for a hand-held circular saw, the sawhaving a circular blade and a substantially planar base for supportingThe saw on a workpiece, the assembly comprising:an upper guard fixedlysecured to the saw and surrounding the upper periphery of the blade,said guard having an opening therein adjacent a forward half of theblade; and a transplant member adapted to be attached to said upperguard adjacent a forward half of the blade, said member being mounted tosaid upper guard to cover said opening, said member having a topsurface, a forward edge, and a rearward edge; wherein said member ismounted to said upper guard in an orientation such that said top surfaceof said member slopes downwardly from said rearward edge to said forwardedge to form a rearwardly facing acute angle with respect to the planarbase, said angle having a minimum value which reduces glare fromoverhead light sources that is the value of a bisecting angle of anangle formed by a first line extending from a first point where theperiphery of the blade exits the top of the workpiece to said rear edgeof said top surface of said member and a second line extending forwardlyfrom said rear edge and parallel to said planar base; said rearwardlyfacing acute angle has a maximum value which reduces glare from forwardlight sources that is the value of a bisecting angle of an angle formedby said first line and a third line that extends a second point sixinches directly front of said first point to said rear edge, of saidmember.
 2. The window assembly of claim 1 wherein said first point isdetermined when the blade is at its maximum cutting depth.
 3. The windowassembly of claim 1 wherein said transparent member is generally planar.4. A window assembly for a hand-held circular saw, the saw having acircular blade and a substantially planar base, the assemblycomprising:an upper guard secured to the saw and surrounding the upperperiphery of the blade, said guard having an opening therein adjacent aforward half of the blade; and a transparent member adapted to beattached to said upper guard adjacent a forward half of the blade, saidmember being mounted to said upper guard to cover said opening, saidmember having a forward edge and a rearward edge; wherein said member ismounted to said upper guard in an orientation such that said memberslopes downwardly from said rearward edge to said forward edge to form arearwardly facing acute angle with respect to the planar base, andwherein said forward edge of said member is placed at a horizontallocation on the upper guard that is rearward of a point where apredetermined line intersects the guard, said line being the tangentline of the point where the blade exits the periphery of the workpiece.5. The window assembly of claim 3 wherein said exit point of said bladeis determined when the blade is at its maximum cutting depth.
 6. Thewindow assembly of claim 4 wherein said transparent member is generallyplanar.
 7. A hand-held circular saw having a circular blade and asubstantially planar base for supporting the saw on a workpiece, the sawcomprising:an upper guard fixedly secured to the saw and surrounding theupper periphery of the blade, said guard having an opening thereinadjacent a forward half of the blade, said guard also having atransparent member covering said opening, said member having a topsurface, a forward edge, and a rearward edge; wherein said member isoriented such that said top surface of said member slopes downwardlyfrom said rearward edge to said forward edge to form a rearwardly facingacute angle with respect to the planar base, said angle having a minimumvalue that is the value of a bisecting angle of an angle formed by afirst line extending from a first point where the periphery of the bladeexits the top of the workpiece to said rear edge of said top surface ofsaid member and a second line extending forwardly from said rear edgeand parallel to said planar base, said angle having a maximum value thatis the value of a bisecting angle of an angle formed by said first lineand a third line that extends from a second point six inches directly infront of said first point to said rear edge of said member.